“The Secret” tells readers toconstantly generate positive brain waves, or be doomed to a life half-lived.

“The Secret” tells readers toconstantly generate positive brain waves, or be doomed to a life half-lived.

“IF you can’t say something good about someone,” a wise woman once said, “sit right here by me.”

Alice Roosevelt Longworth, daughter of Teddy and notorious curmudgeon, would have been awfully lonely if she’d come up with that personal motto during the past decade.

America’s mania for “The Secret,” team-building exercises, Oprah, vision boards, life coaches, antidepressants and inspirational terminal-illness ribbons has all but outlawed any manner of negative thought.

According to this philosophy, if you’re not constantly generating positive brain waves, you’re dooming yourself to a life half-lived, and you deserve whatever hardships may come your way (obviously, as you’re the one who psychically invited them in).

But recently, there’s been an undercurrent of doubt. It seems a perkiness backlash may be brewing, fueled not by hopeful thoughts but by actual scientific research.

In his study “Think Negative!,” published this month in Australian Science, psychology professor Joseph Forgas says bad moods are actually useful for us.

“Mild negative mood and sadness have definite advantages when it comes to dealing with certain kinds of problems that require vigilance, concentration and careful attention to the world around us,” Forgas says via e-mail from the University of New South Wales.

“Our studies specifically suggest that those in a mild negative mood remember more details in their environment, have better eyewitness memories, are less prone to judgmental errors, are less gullible, and are better communicators and persuaders.”

The grouchy and therefore less gullible might also be less inclined to buy into the booming self-help industry, which Barbara Ehrenreich takes down in her new book “Bright-sided: How the Relentless Promotion of Positive Thinking Has Undermined America.”

In her examination of the positive-psychology industry, which she dates back to Norman Vincent Peale’s 1952 book “The Power of Positive Thinking,” Ehrenreich finds that it bears an alarming resemblance to brainwashing.

“We have seen the enemy,” she writes, “and it is ourselves, or at least our thoughts. Fortunately, though, thoughts can be monitored and corrected until .¤.¤. positive thoughts become ‘automatic’ and the individual becomes ‘fully conditioned.’¤”

But fully conditioned to accomplish what?

The millions of adherents of positive thinking have yet to experience a mass increase in wealth, health and happiness. Why haven’t they visualized us out of the current economic climate?

Maybe what we need instead is a little realistic thinking — hell, maybe even a little depression. Instead of hewing rigidly to the mantra “Yes we can!” perhaps we should at least consider what happens if, you know, we can’t.

In a recent article in Scientific American, evolutionary psychologist Paul W. Andrews argues that even full-blown depression isn’t necessarily the disorder it’s been made out to be. Rather, it’s a rational, evolved human response to adverse circumstances.

“Depression is actually an indicator of how much of your intellectual capacity you’re using,” he says.

And intellect has been in short supply during the positive-psychology years, Ehrenreich points out. Books such as “The Secret” and mass-media preachers like Joel Osteen encourage their followers to think of the universe as a big mind-controlled ATM. Success in life is not predicated on educating oneself or learning to think things through — it’s simply a matter of wanting stuff hard enough.

“Anyone, anyone at all could be catapulted into wealth at any time simply by focusing their thoughts,” as Ehrenreich puts it.

In a similar vein, costly personal-enhancement seminars, such as those run by Landmark Corp., have been proliferating wildly. One recent event ended badly enough to have dealt a potentially lethal blow to the whole industry, when three attendees at a $9,000 “Spiritual Warrior” retreat died in an overheated sweat lodge.

Retreat leader James Arthur Ray is the author of the 2008 best seller “Harmonic Wealth: The Secret of Attracting the Life You Want” (the tenets of which are also included in “The Secret”). His tactics, as reported by participants, included encouraging people to push past their limits — even, it seemed, their need for oxygen.

But he’s only the most high-profile member of a massive industry, built on teaching people to stop thinking critically and start hoping. And it’s this kind of pernicious “positive thinking” that researchers like Forgas hope to combat with their findings.

“Vigilant realism is probably a better recipe for success in life than the unrelenting pursuit of positive thinking, which by definition produces a distortion of reality,” he says. “It’s rather strange that American culture has such a simple-minded commitment to positivity.”